Question

请查看下面显示的样本非规范化DB：

|----|---------------|---------|------------------------|---------------|----------------------|
| id | continent     | country | state                  | city          | street               |
|----|---------------|---------|------------------------|---------------|----------------------|
| 1  | North America | USA     | California             | San Francisco | Broadway             |
| 2  | South America | Brazil  | Sao Paulo              | Campinas      | R. Dr. Emilio Ribas  |
| 3  | South America | Brazil  | Sao Paulo              | Campinas      | R. Dr. Vieira Bueno  |
| 4  | Asia          | India   | Maharashtra            | Mumbai        | C.S.                 |
| 5  | Asia          | India   | Maharashtra            | Mumbai        | S.V.                 |
| 7  | Europe        | Germany | North Rhine-Westphalia | Duisburg      | Essenberger          |
| 8  | Europe        | Germany | North Rhine-Westphalia | Bochum        | Solingen             |
| 9  | Europe        | France  | Lorraine               | Toul          | Dijon                |
| 10 | Europe        | France  | Lorraine               | Verdun        | 50 Avenue            |
| 11 | North America | USA     | Massachusetts          | Boston        | Saint Alphonsus      |
| 12 | North America | Canada  | Ontario                | Kingston      | 1st Avenue           |
| 13 | North America | Canada  | Ontario                | Kingston      | 7th Avenue           |
| 14 | North America | Canada  | British Columbia       | Kamloops      | Albert               |
| 15 | North America | USA     | Massachusetts          | Boston        | Eliot                |
|----|---------------|---------|------------------------|---------------|----------------------|

每个下拉列表的值来自上面显示的数据库。街道的价值取决于城市的价值，城市的价值取决于国家的价值，国家的价值取决于国家和国家的价值取决于大陆的价值。

例如：如果我选择北美作为大陆，那么国家/地区的下拉列表应仅显示美国和加拿大。接下来，如果我选择USA，那么State的下拉菜单应该只显示加利福尼亚州和马萨诸塞州等等。当使用jquery / JSP / Servlet对数据库进行非规范化时，有谁能帮助我实现解决方案？

截至目前，我已完成以下编码。我使用了jquery并编写了一个jsp：

<%@ page pageEncoding="UTF-8" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html>
<html lang="en">
    <head>
        <title>Dependent Dropdown</title>
        <script src="http://code.jquery.com/jquery-latest.min.js"></script>
        <script>
            $(document).ready(function() {
                $('#continent').change(function() { fillOptions('country', this); });
                $('#country').change(function() { fillOptions('state', this); });
                $('#state').change(function() { fillOptions('city', this); });
                $('#city').change(function() { fillOptions('street', this); });
            });
            function fillOptions(childID, parentID) {
                var child = $('#' + childID);
                $.getJSON('json/options?child=' + childID + '&val=' + $(parentID).val(), function(opts) {
                    $('>option', child).remove(); // Clean old options first.
                    if (opts) {
                        $.each(opts, function(key, value) {
                            child.append($('<option/>').val(key).text(value));
                        });
                    } else {
                        child.append($('<option/>').text("Please select parent"));
                    }
                });
            }
        </script>
    </head>
    <body>
        <form>
            <select id="continent" name="continent">
                <c:forEach items="${continent}" var="option">
                    <option value="${option.key}" ${param.continent == option.key ? 'selected' : ''}>${option.value}</option>
                </c:forEach>
            </select>
            <select id="country" name="country">
                <option>Please select parent</option>
            </select>
            <select id="state" name="state">
                <option>Please select parent</option>
            </select>
            <select id="city" name="city">
                <option>Please select parent</option>
            </select>
            <select id="street" name="street">
                <option>Please select parent</option>
            </select>
        </form>
    </body>
</html>

Servlet后面的/json/options看起来像：

import java.io.IOException;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.log4j.Logger;
import com.google.gson.Gson;
import com.amey.dao.AddressDAO;
import com.amey.dao.AddressDAOImplementation;

@WebServlet("/CascadingDropdownController")
public class CascadingDropdownController extends HttpServlet {
    private static final Logger LOG = Logger.getLogger( CascadingDropdownController.class.getName() );
    private AddressDAO dao;
    private static final long serialVersionUID = 1L;

    public CascadingDropdownController() {
            dao = new AddressDAOImplementation();
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        LOG.info("In doGet ");
        String child = request.getParameter("child"); // ID of child DD to fill options for.
        String val = request.getParameter("val"); // Value of parent DD to find associated child DD options for.
        Map<String, String> options = null;
        try {
            options = dao.find(child, val);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        String json = new Gson().toJson(options);
        response.setContentType("application/json");
        response.setCharacterEncoding("UTF-8");
        response.getWriter().write(json);
    }
}

老实说，我不清楚DAO的错位。我需要有关DAO逻辑的帮助。

Answer 1

不同的大陆名单：

 SELECT t.continent
   FROM mysqltable t
  GROUP
     BY t.continent

特定大陆的不同国家名单：

 SELECT t.country
   FROM mysqltable t
  WHERE t.continent = 'North America'
  GROUP
     BY t.continent
      , t.country

特定大陆和国家的不同州名单：

 SELECT t.state
   FROM mysqltable t
  WHERE t.continent = 'North America'
    AND t.country   = 'Canada'
  GROUP
     BY t.continent
      , t.country
      , t.state

使用JSP，Servlet，JQuery和非规范化Mysql表的依赖动态下拉列表

1 个答案: